RESEARCH & RELATED Other Project Information: Section 7 (Project Summary) Multicentric lymphoma is the most common cancer in dogs. The current standard of care consists of off-label generic chemotherapy drug regimens. There are no fully approved drugs for the treatment of lymphoma in dogs. Additionally, while multi- or single-agent treatment protocols frequently result in remission of disease, eventually all dogs will relapse. When relapse occurs, clinicians must utilize different cytotoxic agents, preferably agents with distinctive mechanism of action. TANOVEA-CA1 (rabacfosadine for injection), is a double prodrug of the acyclic nucleotide phosphonate PMEG, preferentially targets lymphoma cells with reduced systemic toxicity and has shown potential in dogs that have never been treated as well as those no longer responding to single or multi-agent chemotherapy regimens. TANOVEA-CA1 is conditionally approved by the FDA (NADA 141-475) for the treatment of lymphoma in dogs. This study is being conducted to demonstrate substantial evidence of effectiveness in order to fulfill the pivotal data requirements for the new animal drug application effectiveness technical section in order to receive full approval. The study will be a randomized, multi-center, double-blinded, placebo-controlled study evaluating TANOVEA-CA1 at 1.0 mg/kg every three weeks for up to five treatments in dogs with lymphoma. The primary outcome variable will be progression free survival time as compared to the placebo control group. The secondary outcome variables are: overall response rate, best overall response rate and progression free percentage one month following completion of Cycle 5 (Month 4). Additionally, safety data, including the type and severity of adverse events, will be collected.